Hi there, some men use porn purely for the "filth" factor, even though they are in loving relationships.
Personally i think that sucks.
I think you should talk to him about this, i would not call it cheating exactly, but i would call it disrespectful, hurtful and from what you have said, totally un necessary.
Porn is cold, porn is unreal but love and a good relationship are not.
You deserve better, dont settle for anything less.